help w/ c/c++ problem

[Heinrich Pumpernickel]

28b (macros). write a macro, sizeof(var), that returns the size of
its argument . you are not allowed, to use the sizeof() operator for
this . for extra credit, write another macro, sizeof_t(type), that
returns the size of a type .

given is the following template....... ...

//////////////////////////////////////////////////////////////////////
// ASS28B.C
//////////////////////////////////////////////////////////////////////

#include <Stdio.H>

#define SIZEOF( var ) // FILL IN MACRO TEXT

void main()
{
char a;
short b;
int c;
long d;
long long e;
struct x* (*f)(struct y*);
union { int a[100]; float b[100]; } g;
void* h;

printf("sizeof a : %i\n", SIZEOF(a));
printf("sizeof b : %i\n", SIZEOF(b));
printf("sizeof c : %i\n", SIZEOF(c));
printf("sizeof d : %i\n", SIZEOF(d));
printf("sizeof e : %i\n", SIZEOF(e));
printf("sizeof f : %i\n", SIZEOF(f));
printf("sizeof g : %i\n", SIZEOF(g));
printf("sizeof h : %i\n", SIZEOF(h));
}

//////////////////////////////////////////////////////////////////////
can u hlp me w/ this ?

tnx !!!
--
mfg, heinrich :)

[Army1987]

"Heinrich Pumpernickel" <la****@linuxma il.orgha scritto nel messaggio news:11******** **************@ n2g2000hse.goog legroups.com...

On Jul 1, 5:04 am, Richard Heathfield <[e-mail].i nvalidwrote:

>Heinrich Pumpernickel said:

void main()

If your instructor gave you this template, you need a new instructor. In
C, main returns int.

i dont believe that . my c/c++ teacher (very experienced programmer)
AND the book were using both say that if main does not return a
value it can be declared void !

Both your C/C++ teacher (is he actually teaching you both two
languages?) and the book you're using are wrong.

[Richard Heathfield]

Army1987 said:

>
"Richard Heathfield" <rj*@see.sig.in validha scritto nel messaggio
news:-8************** *************** *@bt.com...

>Heinrich Pumpernickel said:

>>On Jul 1, 5:04 am, Richard Heathfield <[e-mail].i nvalidwrote:
Heinrich Pumpernickel said:

28b (macros). write a macro, sizeof(var), that returns the size
of its argument .

#define SIZEOF(x) (sizeof(x))

but i m not allowed to do that
you are not allowed, to use the sizeof() operator for this .

Why not? That's what it's *for*.

well its just an excersise

I hope that the point of the exercise is to demonstrate that there is
no satisfactory, portable solution to the problem, other than to
change the rules and allow use of the sizeof operator.

You can just about do it for objects:

#define SIZEOF(x) ((unsigned char *)(&(x)+1)-((unsigned char *)&(x))

I've tried
#define SIZEOF(x) ((unsigned char*)(&(x)+1)-((unsigned char*)&(x))
#include <stdio.h>
int main(void)
{
register int x = 23;
printf("%d %d\n", (int)sizeof(x), (int)SIZEOF(x)) ;
return 0;
}
on my DS9K, and something very strange happened...

Yes, because you can't take the address of a register. I deduce (from
the fact that you posted at all) that you survived the experience - or
did your machine post the article on your behalf, posthumously?

Anyway, your point is valid - register objects are Yet Another Reason
Not To Do This Very Silly Thing.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Army1987]

"Richard Heathfield" <rj*@see.sig.in validha scritto nel messaggio news:P-*************** *************** @bt.com...

Army1987 said:

>I've tried
#define SIZEOF(x) ((unsigned char*)(&(x)+1)-((unsigned char*)&(x))
#include <stdio.h>
int main(void)
{
register int x = 23;
printf("%d %d\n", (int)sizeof(x), (int)SIZEOF(x)) ;
return 0;
}
on my DS9K, and something very strange happened...

Yes, because you can't take the address of a register. I deduce (from
the fact that you posted at all) that you survived the experience - or
did your machine post the article on your behalf, posthumously?

Anyway, your point is valid - register objects are Yet Another Reason
Not To Do This Very Silly Thing.

To be honest, the DS9K was actually MSVC, and the "something very
strange" was that it didn't compile. (The requirement for the
operand of & not to be register is a constraint.)

But I'm thinking of replacing it with:
#include <stdio.h>
#define SIZEOF(x) ((unsigned char*)(&(x)+1)-((unsigned char*)&(x))
int main(void)
{
int x = 23;
int *p = &x;
printf("%d\n", (int)SIZEOF(*p+ +));
return 0;
}
and running it on a DS9K. But I'm too afraid to do that.

[CBFalconer]

Heinrich Pumpernickel wrote:

<[e-mail].i nvalidwrote:

>Heinrich Pumpernickel said:

.... snip ...

>>

>>void main()

If your instructor gave you this template, you need a new
instructor. In C, main returns int.

i dont believe that . my c/c++ teacher (very experienced
programmer) AND the book were using both say that if main does
not return a value it can be declared void !

Then both the book AND your instructor are wrong, and both need
replacing.

--
<http://www.cs.auckland .ac.nz/~pgut001/pubs/vista_cost.txt>
<http://www.securityfoc us.com/columnists/423>
<http://www.aaxnet.com/editor/edit043.html>
cbfalconer at maineline dot net

--
Posted via a free Usenet account from http://www.teranews.com

[Army1987]

"Heinrich Pumpernickel" <la****@linuxma il.orgha scritto nel messaggio
news:11******** **************@ c77g2000hse.goo glegroups.com.. .

>

28b (macros). write a macro, sizeof(var), that returns the size of
its argument . you are not allowed, to use the sizeof() operator for
this .

#define SIZEOF( var ) sizeof var
Note that I used sizeof, without parentheses, not sizeof().

for extra credit, write another macro, sizeof_t(type), that
returns the size of a type .

Does the requirement for the previous point also apply to this one?
If so, the latter point is impossible. If not, try:
#define sizeof_t sizeof

[CBFalconer]

Army1987 wrote:

>

.... snip ...

>
I've tried
#define SIZEOF(x) ((unsigned char*)(&(x)+1)-((unsigned char*)&(x))
#include <stdio.h>
int main(void)
{
register int x = 23;
printf("%d %d\n", (int)sizeof(x), (int)SIZEOF(x)) ;
return 0;
}
on my DS9K, and something very strange happened...

Doesn't need a DS9K. Taking the address of a register variable is
illegal.

--
<http://www.cs.auckland .ac.nz/~pgut001/pubs/vista_cost.txt>
<http://www.securityfoc us.com/columnists/423>
<http://www.aaxnet.com/editor/edit043.html>
cbfalconer at maineline dot net

--
Posted via a free Usenet account from http://www.teranews.com

[Army1987]

"CBFalconer " <cb********@yah oo.comha scritto nel messaggio news:46******** *******@yahoo.c om...

Army1987 wrote:

>>

... snip ...

>>
I've tried
#define SIZEOF(x) ((unsigned char*)(&(x)+1)-((unsigned char*)&(x))
#include <stdio.h>
int main(void)
{
register int x = 23;
printf("%d %d\n", (int)sizeof(x), (int)SIZEOF(x)) ;
return 0;
}
on my DS9K, and something very strange happened...

Doesn't need a DS9K. Taking the address of a register variable is
illegal.

If it wasn't illegal, nothing strange would happen even on a DS9K,
since the DS9K is a conforming hosted implementation.

[Mark McIntyre]

On Sat, 30 Jun 2007 20:15:03 -0700, in comp.lang.c , Heinrich
Pumpernickel <la****@linuxma il.orgwrote:

>On Jul 1, 5:04 am, Richard Heathfield <[e-mail].i nvalidwrote:

>Heinrich Pumpernickel said:

well its just an excersise

OK, but in that case I suggest you write your best effort at solving
the problem, post it here, and ask for assistance. You could also
google for it.

>If your instructor gave you this template, you need a new instructor. In
C, main returns int.

i dont believe that . my c/c++ teacher (very experienced programmer)
AND the book were using both say that if main does not return a
value it can be declared void !

Then I'm afraid that both your book and your teacher are wrong. The C
Standard REQUIRES main to return an int. Whether you want to return
something or not, you need to at least return 0. Otherwise you are
breaking the rules of C.

--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan

[Harald van =?UTF-8?B?RMSzaw==?=]

Mark McIntyre wrote:

Then I'm afraid that both your book and your teacher are wrong. The C
Standard REQUIRES main to return an int.

This is incorrect. The C standard requires implementations to accept main
returning int, but does not prohibit other return types either from being
allowed by implementations or from being used by programs.

[Richard Heathfield]

Harald van D?k said:

Mark McIntyre wrote:

>Then I'm afraid that both your book and your teacher are wrong. The C
Standard REQUIRES main to return an int.

This is incorrect. The C standard requires implementations to accept
main returning int, but does not prohibit other return types either
from being allowed by implementations or from being used by programs.

True enough, but neither does it define the behaviour of such program.
The C Standard does not forbid implementations from accepting Fortran
programs, either. That doesn't mean that Fortran programs are correct C
programs.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999